best way is to get your feet wet (and maybe your face too) if you go to LCS and shared asset library (not in your project) you will notice under BI where you can download that sales report to your local Dev VM (cloud hosted or on premise). After you have downloaded this to your dev vm then go to D365 > Sysadmin > setup > Entity Store (or type it in the search in D365) and you can then setup the sales cube by clicking edit, then set the refresh to something like 1 per month, then click refresh.
the data is then pushed into your local SQL AxDW database and if you then open the sales cube you will notice it connects and fully displays the report and data model (you can separate these)
every client i go out and push almost all of these entity store cubes out to the AxDW, download all the power bi dashboards and open them up and start displaying them and modifying them.
That particular report has INVOICE LINES, PRODUCTS and SALES CATEGORIES with some great measures for gross margin, gross margin current year and gross margin last year same goes for revenue so the calcs are mostly done for you. SALES CATEGORIES is mostly used like slicer here (should be a slicer)